Recirculating burner



B. R. WALSH ET AL Jan. 30, 1968 RECIRCULATING BURNER 4 Sheets-Sheet 1 Filed Aug. 1, 1966 S mun T S w M L V E A A V W D mRA E S Cll U V R R B O Jan. 30, 1968 B. R. WALSH ETAL 3,366,154

RECIRCULATING BURNER Filed Aug. 1, 1966 4 Sheets-Sheet 2 INVEINTORS BRUCE R. WALSH FIG. 6

ORVIS A. DAVIS, SR.

Jan. 30, 1968 B. R. WALSH ETAL RECIRCULATING BURNER 4 Sheets-Sheet 3 Filed Aug. 1, 1966 FIG. 7

FIG. 8

FIG. 9

INVENTORS BRUCE R. WALSH ORVIS ,A. DAVIS, SR.

Jan. 30, 1968 B. R. WALSH ETAL 3,366,154 REGIRCULATING BURNER Filed Aug. 1, 1 966 4 Sheets-Sheet 4 q 596% ii (D 15% 0a 0 w w 0 0; an 0 (w w wgw 320E 0 II 0 14 3 2; 2 a OD ll FIG-i2 INVENTORS BRUCE R. WALSH ORVIS A. DAVIS, SR.

United States Patent 3,366,154 RECIRCULATING BURNER Bruce R. Walsh, Fittsburgh, and Orvis A. Davis, Sn,

Gibsonia, Pa., assignors to Gulf Research & Development Company, Pittsburgh, Pa., a corporation of Delaware Filed Aug. 1, 1966, Ser. No. 569,386 18 Claims. (Cl. 1581) AESTRACT OF THE DISCLOSURE A compact portable burner useful in flame cultivation of crops, comprising an elongated hollow body formed with a venturi throat, and a recirculation jacket surrounding the body from the throat to the front end. The body wall is formed with recirculation entrance openings at the front end, and with recirculation exit openings at the venturi throat to recirculate products of combustion. A nozzle is positioned at the openings at the venturi throat.

This invention relates to burners, paricularly adapted for use in flame weeding, and other applications wherein a clean flame substantially free of unburned fuel and hot carbon particles is desirable; and which are adapted to burn oil as the fuel,

The technique of flame cultivation for the control of weeds in crops such as cotton, corn, grain sorghum, etc., has been extensively studied and developed in recent times. However, most commercially available burners designed for this purpose use liquefied petroleum gas (LPG) as the fuel. However, LPG is undesirable as a fuel for several reasons, for example; the fear of fire and explosion in its use and storage, its higher cost in some areas as compared to the cost of fuel oil, and its unavailability in certain areas.

Therefore, it is an object of this invention to provide a burner of the character described which is at least as efficient in its operation as LPG burners heretofore available, while avoiding the use of LPG and preferably using oil, as fuel.

Another object of this invention is to provide a burner of the character described comprising means to utilize the venturi principle to cause recirculation of some of the products of combustion from the discharge end of the burner back to the vicinity of the nozzle, at which vicinity the venturi throat is located, to provide a heated secondary air supply, to cause improved vaporization of the fuel oil, to cause increased turbulence in the air-oil mixture for more eflicient mixing, and to provide a clean flame.

The above and other objects and advantages of the present invention will in part become apparent and will in part be pointed out in the following detailed description, reference being bad to the accompanying drawing forming a part thereof in which:

FIG. 1 is a front elevational view of a burner embodying the invention;

FIG. 2 is a rear elevational view thereof;

FIG. 3 is a side elevational view thereof;

FIG. 4 is a bottom plan view thereof;

FIG. 5 is a cross-sectional view taken on line 5-5 of 7 FIG. 3;

FIG. 6 is a cross-sectional view taken on line 66 of FIG. 4;

FIG. 7 is a partial perspective view of a detail;

FIG. 8 is a front elevational view of a first modified construction;

FIG. 9 is a cross-sectional view taken on line 9--9 of FIG. 8;

FIG. 10 is a front elevational view of a second modified construction; and

FIGS. 11 and 12 are cross-sectional views taken on lines 11-11 and 12-12 of FIG. 10 respectively.

Referring now in detail to the drawing, 10 designates a burner embodying the invention. Burner 10 comprises top and bottom walls 12 and 14 respectively, and a pair of similar, symmetrically disposed side walls 16 joining the longitudinal edges of the top and bottom walls. Walls 12, 14, and 16 extend the entire length of burner 10, to provide an axial opening therethrough.

Means are provided to provide recirculation of some of the products of combustion from the discharge end of the burner to a position mediately the end thereof at the venturi throat and just forwardly of the face of the nozzle, as will appear more clearly below, for the purposes of providing a clean flame and more eflicient burning of fuel, to provide improved vaporization of fuel, greater turbulence, and similar advantages. To this end, a recirculation jacket 18 surrounds this portion of the burner, and comprises a top wall 20, a bottom wall 22, and a pair of similar symmetrically disposed side walls 24, joining the ends of walls 20 and 22. Walls 20, 22, and 24 are similar in configuration to the adjacent portions of and are in a predetermined outwardly spaced relation to, walls 12, 14, and 16, respectively. The front ends of the jacket walls and the burner walls are joined together by a front shoulder 26. The rear ends of the jacket walls 12, 14, and 16 at a predetermined position along the axis of the burner rearwardly of the venturi throat, by a rear shoulder 28. Walls 12, 14, and 16 are provided with a plurality of openings 30 adjacent and slightly rearwardly of front shoulder 26, and with a plurality of openings 32 adjacent and slightly forwardly of rear shoulder 28. Openings 30 and 32 may be plain circular openings, such as openings 60 and 62 in the second embodiment of FIGS. 8 and 9, or may have offset edges on one side as in the embodiments of FIGS. 1 to 7, and openings and 132 in FIGS. 10 to 12. The openings 30 are arranged in four rows around the front of the burner, and openings 32 are arranged in two rows at the venturi throat of the burner. More openings are provided at the front than at the throat to accommodate the increase in volume of the burning air and oil at the discharge end of the burner, and because of physical limitations of locating openings in the venturithroat. The beginning of the flame is located within the discharge end of the burner at about the loca tion of openings 39.

Referring to FIG. 7, it will be seen that each opening 30 has a raised offset portion 34 at the front side of the opening. Portion 34 acts a scoop with respect to the combustion passing over these openings. Openings 32 are similar in structure to openings 30, but the rear openings have their offset portions 36 disposed at the rear of the openings, since the recirculated combustion products must exit from these openings after having entered openings 30 and recirculated through jacket 18, back into the main stream passing through the burner. Offset portions 36 are depressed into the recirculation jacket to scoop combustion products passing over them.

A pair of threaded sleeves 38 are mounted in suitable openings formed in walls 14 and 22, and receive any suitable ignition means, such as as electrodes or a spark plug in which event only one sleeve 38 would be provided. Sleeves 38, while they are positioned in the recirculation chamber, are small enough so that they present a negligible obstruction to the flow of gases therein.

Burner 10 is a self-contained, compact unit, and can be mounted in any suitable manner, such as by a bracket secured to any external wall.

Referring to FIG. 5 it will be seen that side walls 16 flare outwardly both forwardly and rearwardly from a narrowed throat portion which is located in spaced relation to the front end of the burner, and which functions Patented Jan. 30, 1968 t as the venturi. Referring to FIG. 6, it will be seen that walls 12 and 14 are flat and slope towards each other from rear to front over their entire length, thus defining a larger space between them at their rear ends, and a smaller space between them at their front ends. The walls 20, 22, and 24 of jacket 18 follow the curvature or inclination of the respective portions of walls 12, 14, and 16, respectively, between the front and rear shoulders 26 and 28. Thus, burner functions as a venturi in a horizontal plane, and functions as a nozzle in a vertical plane, which structure tends produce a vertically compressed and horizontally spread flame which is particularly adapted for use in flame weeding, and other applications such as bakery ovens, kilns, and the like. The outwardly flaring configuration of walls 16 and the spreading configuration of walls 12 and 14 rearwardly of rear shoulder 28 create increasing rectilinear cross-sectional areas rearwardly of said shoulder, which provides for a large intake of secondary air through the rear end of the burner, and which enhances the operation of the venturi.

Burner 10 could be used with many fuels, but advantageously, oil is used for the reasons set forth above. Means are provided to mount a fuel oil nozzle at the venturi throat. To this end, four struts 42 are provided, each having its outer end joined to one of the Walls 12, 14, or 16, and its inner end joined to a nozzle mounting collar 44. Mounted and suitably secured in collar 44 by any suitable means is a nozzle 46 which is joined to a fuel oil supply pipe 48, and a primary air supply pipe, now shown, if necessary. It has been found that burner 10 embodying this first form of the invention works most efficiently when nozzle 46 is of the type which produces a flat spray. The nozzle disclosed in US. patent application Ser. No. 524,672, filed Feb. 3, 1966, entitled, Nozzle, by Orvis A. Davis, Sr., and assigned to the same assignee as the present invention, has produced satisfactory results when used with burner 10 in flame weeding of crops.

Referring to FIGS. 8 and 9 there is shown a burner 50, comprising a second embodiment. Burner 50 comprises a wall 52 flaring outwardly both forwardly and rearwardly from a throat or venturi, similar to the structure of burner 10 in a horizontal plane, as shown in FIG. 5. A recirculation jacket 54 surrounds wall 52 betwen the front end of the burner and the throat, and is supported thereon in spaced relation thereby by a front shoulder 56 and a rear shoulder 58. Wall 52 is provided with a plurality of openings 60 arranged in four rows adjacent the discharge end of the burner, and with a single row of openings 62 adjacent the throat, for the same reasons explained above regarding openings and 32. In place of the single row 62, two or more rows could be provided for increased circulation, if necessary, depending on the nozzle used.

A nozzle 64, mounted on a supply pipe 66, has its front end positioned adjacent openings 62. The nozzle is held in burner 50 by means of a set screw collar 68 to which are joined three struts 70, each having its outer end secured to the rear end of burner 50 by any suitable means such as screws 72. Burner 50 will produce a conical flame which will have its combustion products recirculated just as combustion products of burner 10 are recirculated. Burner 50 is suitable for use in applications where the flat flame produced by burner 10 is not the most desirable flame, such as in a water boiler or furnace where it is desirable to have a flame which is shaped to suit the combustion space available; for example, where there is no firebox.

Referring to FIGS. 10 to 12. there is shown a burner 100, comprising a third embodiment. Burner 100 is smiliar to burner 10 of FIGS. 1 to 7, and similar parts are indicated by the same reference numeral increased by 100. The nozzle, the struts, or other means mount the nozzle with its front face in the vicinity of the venturi throat and rear openings 136, and the ignition means mounting sleeves analogous to sleeves 38, have been omitted from are present in the actual burner, and may be the same as the analogous parts of the first two embodiments.

Comparison of FIGS. 5 to 11 show that side walls 16 and 116 are similar in configuration, and the burner is about the same as burner 10 in a horizontal plane.

Comparison of FIGS. 6 and 12 shows that top and bottom walls 112 and 114 flare outwardly away from each other both forwardly and rearwardly from the area of rear openings 132, which is the area of the venturi throat. Top and bottom walls 12 and 14 of burner 10 are flat and slope towards each other over their entire length from rear to front, as described above. Thus, the major difference between burners 10 and 100 is that burner 100 functions as a venturi in both the horizontal and vertical planes to produce a rectangular flame spread both vertically and horizontally.

Just as in burner 10, the walls 120, 122, and 124 of recirculation jacket 118 of burner follow the curvature of the respective portions of walls 112, 114, and 116, respectively, between front and rear shoulders 126 and 128.

Burner 100 is suitable for use in many applications such as flame weeding of crops, and boilers or furnaces wherein the combustion space available is better suited to the flame of burner 100 than to the flame of burner 50. In flame weeding applications the choice of burner will be determined by the particular nature of the crop and weed combination to be flamed, as will be evident to those skilled in the art.

While the invention has been described in some detail above, it is to 'be understood that the protection granted is to be limited only within the spirit of the invention and the scope of the following claims.

We claim:

1. A self-contained burner comprising an elongated hollow body having front and rear axially aligned open ends to permit the passage of ambient air therethrough, said body comprising longitudinal continuous wall means Whose ends define said front and rear openings, the volume within said hollow body defined by said wall means being symmetrical about planes containing the longitudinal axis of said body, said wall means defining a narrowed throat portion within said hollow body in spaced relation to the open front end thereof, and means to recirculate fluids passing through said body from points located closely adjacent to and rearwardly of said front open end to points located substantially at and forwardly of said throat portion.

2. The combination of claim 1, said recirculation means comprising jacket means surrounding said wall means from said open front end to said throat portion, said jacket means comprising a jacket wall spaced from said wall means and a pair of jacket end walls interconnecting the ends of said jacket wall and said wall means, to define a single recircultaion chamber between said jacket means and said portion of said wall means, said recirculation means further comprising a first plurality of openings formed in said wall means adjacent said open front end communicating said recirculation chamber with the space within said body adjacent said front open end, and a second plurality of openings formed in said wall means adjacent said throat portion communicating the space within said body adjacent said throat portion with the rear of said recirculation chamber.

3. The combination of claim 2, the portions of said wall means surrounding each of the openings of said first and second plurality of openings being offset from the plane of said wall means on one side of each of said openings.

4. The combination of claim 1, the volume defined by said wall means being substantially rectilinear in all planes perpendicular to said axis.

5. The combination of: claim 1, the volume defined by said wall means being substantially circular in all planes perpendicular to said axis.

6. The combination of claim 1, said wall means comprising a first pair of flat, horizontally disposed walls inclined towards each other from said throat portion towards said open front end and a second pair of curved vertically disposed walls joining the longitudinal edges of said horizontal walls and flaring outwardly from said throat portion towards said open front end, whereby a flame issuing from said burner is of rectangular shape and vertically compressed and horizontally spread out.

7. The combination of claim 1, said wall means driverging apart from said throat portion towards both said open rear end and said open front end, whereby the cross-sectional area of said body increases from said throat portion towards both said open rear end and said open front end.

8. The combination of claim 1, said wall means comprising a first pair of curved horizontally disposed walls flaring outwardly from said throat portion towards said open front end, and a second pair of curved vertically disposed walls joining the longitudinal edges of said horizontal walls and flaring outwardly from said throat portion towards said open front end, whereby a flame issuing from said burner is of rectangular shape and vertically and horizontally spread out.

9. The combination of claim 2, said wall means comprising a first pair of fiat horizontally disposed walls inclined towards each other from said throat portion towards said open front end and a second pair of curved vertically disposed walls joining the longitudinal edges of said horizontal walls and flaring outwardly from said throat portion towards said open front end, whereby a flame issuing from said burner is of rectangular shape and vertically compressed and horizontally spread out.

10. The combination of claim 2, said wall means comprising a first pair of curved horizontally disposed walls flaring outwardly from said throat portion towards said open front end, and a second pair of curved vertically disposed walls adjoining the longituding edges of said horizontal walls and flaring outwardly from said throat portion towards said open front end, whereby a flame issuing from said burner is of rectangular shape and vertically and horizontally spread out.

11. The combination of claim 4, said Wall means comprising a first pair of flat horizontally disposed walls inclined towards each other from said throat portion towards open front end and a second pair of curved vertically disposed walls joining the longitudinal edges of said horizontal walls and flaring outwardly from said throat portion towards said open front end, whereby a flame issuing from said burner is of rectanguar shape and is vertically compressed and horizontally spread out.

12. The combination of claim 1, in combination with fuel oil nozzle means, said burner comprising means to position said nozzle means with the front face of said nozzle means substantially at said recirculation means at said throat portion.

13. The combination of claim 2, in combination with nozzle means, said burner comprising means to position the front face of said nozzle means substantially at said second plurality of openings.

14. The combination of claim 9, said first pair of flat horizontally disposed walls diverging away from each other from said throat portion towards said open rear end, and said second pair of vertically disposed walls flaring outwardly from said throat portion towards said open rear end, whereby the cross-sectional area of said body increases from said throat portion towards both said open rear end and said open front end.

15. The combination of claim 10, said first pair of horizontally disposed walls flaring away from each other from said throat portion towards said open rear end, and said second pair of vertically disposed walls flaring away from each other from said throat portion towards said open rear end, whereby the cross-sectional area of said body increases from said throat portion towards both said open rear end and said open front end.

16. The combination of claim 4, said wall means comprising a first pair of curved horizontally disposed walls flaring outwardly from said throat portion towards said open front end, and a second pair of curved vertically disposed Walls joining the longitudinal edges of said horizontal walls and flaring outwardly from said throat portion towards said open front end, whereby a flame issuing from said burner is of rectangular shape and vertically and horizontally spread out.

17. The combination of claim 2, each opening of said first plurality of openings comprising an offset portion at the side thereof closest to said front open end, and each of said offset portions of said first plurality of openings extending into said hollow body.

18. The combination of claim 17, each opening of said second plurality of openings comprising an offset portion at the side thereof furthest from said front open end, and each of said offset portions of said second plurality of openings extending into said recirculation chamber.

References Cited UNITED STATES PATENTS 2,516,063 7/1950 Logan et al. 158-76 2,701,608 2/1955 Johnson 158-1 2,867,267 1/1959 Nerad et al. 1584 2,918,117 12/1959 Griflin 1581 2,925,858 2/1960 Reed 158-1 3,174,527 3/1965 Reed et al. 158-11 FOREIGN PATENTS 1,129,673 9/ 1956 France.

FREDERICK L. MATTESON, JR., Primary Examiner. E. G. FAVORS, Assistant Examiner, 

